Possible involvement of cytochrome c release and sequential activation of caspases in ceramide-induced apoptosis in SK-N-MC cells.

Ceramide is characterized as a second messenger of apoptosis induced by various agents such as tumor necrosis factor (TNF-alpha), Fas ligand, hydrogen peroxide, heat shock and ionizing radiation. In this study, we investigated the mechanism of ceramide-induced apoptosis using a human neuroblastoma cell line, SK-N-MC. N-Acetyl-sphingosine (C2-ceramide), a cell-permeable ceramide analogue, was able to induce apoptosis in SK-N-MC cells as estimated by DNA fragmentation and chromatin condensation. C2-ceramide-induced DNA fragmentation was blocked by caspase inhibitor (Z-Asp-CH(2)-DCB). An increase in caspase-3 (CPP32)-like protease activity was evident during C2-ceramide-induced apoptosis, suggesting that caspases are involved in this apoptosis. Moreover, enzymatic cleavage of VDVAD-AFC and LEHD-AFC (specific substrates for caspase-2 and -9, respectively) was increased by treatment with C2-ceramide. To elucidate which types of caspase are activated in C2-ceramide-treated cells, we performed Western blot analysis using antibodies against each isoform. Both proforms of caspase-2 and -3 were decreased in response to C2-ceramide in a time-dependent manner. Mitochondrial cytochrome c is also time-dependently released into the cytosol in response to treatment with C2-ceramide. Addition of cytochrome c into the S-100 fractions prepared from SK-N-MC cells could activate caspase-2 in cell-free systems. These results suggest the possibility that cytochrome c released to the cytosol can activate caspases (caspase-9, -3, and -2) during C2-ceramide-induced apoptosis of SK-N-MC cells.

Pyruvate dehydrogenase complex deficiency with multiple minor anomalies.

Pyruvate dehydrogenase complex (PDHC) deficiency is known to cause congenital lactic acidosis. The case of a 9-month-old female infant with PDHC deficiency caused by a mutation in exon 11 of the pyruvate dehydrogenase (PDH) E1 alpha gene is described. Her facial features were as follows: frontal bossing, upslanting palpebral fissures, a short upturned nose, a long philtrum and low set ears. These anomalies are characteristic not only of a malformation syndrome or chromosomal aberration, but also of PDHC deficiency. Because PDHC deficiency requires early treatment, metabolic disorders should be kept in mind in a patient with dysmorphic features. Further, she had multiple minor anomalies including bilateral inguinal herniae, an umbilical hernia and small hands and feet, which have not been described in previous reports.

Ictal HMPAO-single photon emission computed tomography findings in reading epilepsy in a Japanese boy.

Reading epilepsy is rare. We report a 14-year-old right-handed Japanese boy who had had jaw jerking only while reading since age 12 years. The episodes occurred every time he read an English textbook and sometimes during prolonged reading of a Japanese textbook. The jaw jerking evolved to generalized tonic-clonic seizures (GTCS) on only two occasions during prolonged reading aloud. Routine EEGs showed no abnormality. After a few minutes of reading, however, the EEG showed bilateral 2-Hz, 150-microV spike-wave complexes with left frontotemporal accentuation, accompanied by jaw jerking. Ictal single photon emission computed tomography (SPECT) with [99Tc]hexamethylpropylene amine oxime (HMPAO) showed focal hyperperfusion of the frontal lobes bilaterally and of the left temporal area. Interictal SPECT and magnetic resonance imaging (MRI) were normal. The combination of valproate (VPA) and clonazepam (CZP) almost eliminated his symptoms. Ictal SPECT is a useful technique for seizure localization in reading epilepsy.

Serial neuroimages of acute necrotizing encephalopathy associated with human herpesvirus 6 infection.

A previously healthy 8-month-old girl developed exanthem subitum and acute encephalopathy with status epilepticus, quadriplegia and bilateral abducens nerve palsies. Human herpesvirus-6 DNA was found in the cerebrospinal fluid by the polymerase chain reaction at the acute stage. Cranial computed tomography showed low density areas in the thalami and in the cerebellar and abducens nuclei. The distribution of the lesions was consistent with acute necrotizing encephalopathy. As for the thalamic lesions, a T2 weighted magnetic resonance image on the 24th day of the illness demonstrated low signal intensity surrounded by high intensity; 99mTc-ECD SPECT showed hypoperfusion, which suggested irreversible tissue damage. The patient is now 1 year 6 months old and has spastic quadriparesis with mental retardation and abducens nerve palsies.